So it happened that I was starting a contract job, and in turn the first task was to install a nice OS on the machine. So a bootable ISO of FreeBSD was duly downloaded, burned to a CD-ROM, and inserted into the PC I'd been allocated. With the installation nearly complete, we went of to make tea. On return, I realised that I didn't have a drinks coaster. By now, the machine was ready to reboot, from its hard disk. So within the hour, the CD-ROM had a new job :-)